Thomas bakee



UNITED STATES Patented January 19, 1904.

PATENT OFFICE.-

THOMAS BAKER, OF MELBOURNE, VICTORIA, AUSTRALIA.

PROCESS OFPREPARIING QPHOTOGRAP'HIC PRINTS FOR TONING.

SPECIFICATION forming part of Letters Patent No, 750,014, dated January19, 1904.

A li ati fil d November 21, 1902. Serial No. 132,329. (No specimens.)

To all whom it may concern.-

Be it known that I, THOMAS BAKER, a subject of the King of GreatBritain, director of Baker and Rouse Proprietary, Limited, residing atNo. 260 Collins street, Melbourne, in the State of Victoria andCommonwealth of Aus tralia, have invented certain new and usefulImprovements in Processes of Preparing Photographic Prints for Toning,of which the following is a specification.

When toning is to be effected in the case of What are known asprinting-out papers, it is necessary before placing the prints in thetoning-bath to remove from them all the soluble silver salts which theycontain unless the toning is to be effected in what is known as acombined bath, which, however, is not generally employed. The removal ofthe soluble silver salts has hitherto been carried out by washing theprints in many changes of water,

' which is both tedious and troublesome and in vert the soluble silversalt contained in it intoan insoluble silver salt or combination ormix-.ture of insoluble silver salts, and yet leave no injurious excess ofsoluble haloid or haloids in the film, and that the print may after suchtreatment be placed without Washing (or with only sufiicient washing torinse away the superfluous solution of chlorid or other salts from thesurface of the print) directly into the toning-bath, and that the toningwill then go on'much in the same way as if the print had been washed.

I am aware that it has been customary to treat prints with a solution ofa chlorid before toning; but it has always been done with a solution ofsuch strength that an injurious excess of chlorid remained in the printsand the washing of the prints has been equally or even more necessarythan if theyhad not been so treated. I have also found that the additionof an iodid or bromid to such a solution as I have mentioned above has amarked and beneficial influence upon the course of the toning and thatthe high lights of the prints so treated are far less liable to beaffected injuriously in the toning-bath than if the iodid or bromid oreven for some tones a combination of the two had not been employed.

The color of prints treated by iodid in solution previous to toning isless changed by the subsequent operation of fixing than if it had notbeen used, which also is decidedly advantageous.

The solution of the haloids, as mentioned above, may contain withadvantage a substance or combination of substances which has or have theeffect of hardening or tanning gelatin, such as alum of various kinds,salts of aluminium, tannic acid, formol. An excellent combination is asfollows, and it is suitable for most makes of printing-out papers,though it may require adjustment to suit any particular brand. If thereis a milky deposit upon the surface of the prints when they are placedin it, the solution is too weak, and if the toning operation is slowedby it it is too strong, either of which defects may be remedied by usinga little more or less water in making up the solution: chlorid ofsodium, one and one-fourth grains; sulfate of alumina, five grains;water, one fluid ounce; but I do not'confine myself to this exactformula. The prints are dipped into such a solution, allowed to remainin it until they become limp and lie flat, when they are withdrawn andeither placed directly in the toning bath or rinsed with water to washaway the superfluous solution from the surface.

A suitable solution containing iodid is made by replacing portion (say.one-half) or the whole of the chlorid of sodium in the above formulawith its chemical equivalent of iodid of potassium or other solubleiodid.

When a bromid is added, the proportion should not exceed one grain inforty ounces of the solution, as otherwise the toning would berenderedtoo slow.

If iodid alone is used, the toning is also somewhat slow; but bromidalone is too slow for practical purposes.

Having now particularly described and as- 5 certained the nature of mysaid invention and in what manner the same is to be performed, I declarethat what I claim is The herein-described process of preparingphotographic prints for toning, which con- 1 O sists in treating theprints with a solution consisting of chlorid of sodium, sulfate ofalumina and water combined in substantially the proportions described,to convert the soluble silver salt contained in the prints into aninsoluble salt.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

THOMAS BAKER.

Witnesses:

EDWARD WATERS, WILLIAM GUEST HOLDEN.

